Electrical plug-and-socket connection

ABSTRACT

In order to configure an electrical plug-and-socket connection (1) comprising two complementary, latchable housing parts (2, 3) and comprising a sealing member (11) construction with annular lamellae (12, 13) in such a way that it is liquid-tight and its housing parts (2, 3) can be plugged into one another and withdrawn from one another with a low expenditure of force, the annular lamellae (12, 13) are constructed with different diameters (D1, D2) and act in a tapering insertion section (7) of one housing part (2) as a lamella seal and as a compression seal. (FIG. 4.)

The invention proceeds from an electrical plug-and-socket connection inaccordance with the preamble of claim 1.

Such a plug-and-socket connection is disclosed in DE 35 40 831 C2. Theplug-and-socket connection described therein consists of a first and asecond housing part. A hollow cylindrical sealing member, which isarranged on a cylindrical component in one of the two housing parts, haslips of different diameter in an alternating sequence. The larger lipsin this case overlap the socket-shaped insertion section of one of thehousing parts. As a result, these sealing lips are deflected arcuatelyin the axial direction upon coupling of the plug-and-socket connection.The small lips delimit the interspace available for the bent sealinglips, and have no sealing function. The housing parts are locked aftertheir end position is reached.

U.S. Pat. No. 4,946,402 discloses a further such plug-and-socketconnection, whose sealing member likewise has sealing lips of differentdiameter. Both the continuous conical construction of the insertionregion of the first housing part, and the corresponding arrangement ofthe sealing lips cause compression of all the sealing lips between thehousing parts when the plug-and-socket connection is brought together.The sealing principle, applied there, of compression sealing is veryexpensive in terms of force, resulting in-a correspondingly high forcecomponent in the plug-in force. The type of sealing is unsatisfactoryfrom this aspect of optimizing the expenditure of force.

DE-AS 25 55 147 describes a plug-and-socket connection in which thesealing between the housing parts is likewise performed essentiallyaccording to the above-named principle. A hollow cylindrical sealingmember having three radial sealing lips is fastened to a cylindricalcomponent of one housing part. The outside diameter of the three sealinglips is larger than the inside diameter of a socket-shaped housing part,with the result that the lips of the sealing member are deflectedarcuately in the axial direction when the housing parts are pushedtogether. When the plug-and-socket connection is coupled, the air iscompressed and escapes along the inner walls of the socket-shapedhousing part and the outer ends of the sealing lips, the result beingthat the arcuate course is produced thereby and by the oversized lips.Locking of the housing parts does not take place, since the adhesiveproperties of the rubber and the bent sealing lips do not permitinadvertent decoupling. The separating forces increase with the numberof sealing lips.

Moreover, it is known from DE-OS 2745887 to arrange a sealing memberbetween a high-voltage cable and a housing part for the purpose ofproducing a gas-tight connection. After the cable end has been fittedwith the sealing member, it is inserted into the housing part andsecured with a metal sleeve at the rear. A cable receiving opening inthe housing part extends conically in order to permit a simpleinterplugging with the sealing member, which is of beveled construction.Three sealing lips arranged outside on the sealing member ar constructedin accordance with the beveling with a decreasing diameter. The effectof the metal sleeve is, inter alia, that the sealing lips are compressedin the insertion opening and thus ensure tightness.

A further watertight connection is disclosed in U.S. Pat. No. 4,417,736.In this case, a cylindrical housing part is arranged in a socket-shapedhousing part with the inter-position of a seal. The seal encloses thecylinder and is beveled like the cylinder itself in the plug-indirection. The receptacle of the socket-shaped housing part has a formwhich is the complement of this. The sealing member is formed withcompressible lips on the inner and outer walls, which ensure adequatesealing and simultaneously decrease centering problems.

The above-named plug-and-socket connections exhibit the basic principlesof sealing housing parts by means of a sealing member constructed withlips. Depending on the degree of oversizing of the sealing lip diameterwith respect to the inside diameter of the socket-shaped housing part, adeflection of the sealing lip in the axial direction is understood as alamella seal, while pinching of the sealing lip in the radial directionis known as a compression seal.

When the housing parts are interplugged, in addition to the frictionforces for sealing it is necessary to apply further forces which, whenadded, are defined as the so-called plug-in force. Because of thegeneral aim of miniaturization, the ratio of contact parts per surfacearea has increased, and the plug-in force has risen as a result. Theseplug-and-socket connections are difficult to handle during assembly. Thereverse movement, that is to say the drawing apart of the housing parts,is likewise expensive in terms of force, since with a rising number oflamellae the sealing member is sucked tight because of the lack ofpressure balance. Consequently, the sealing principles of the previouslyknown plug-and-socket connections have to be adapted to the morestringent requirements relating to ease of assembly.

It is therefore the object of the invention to configure aplug-and-socket connection according to the preamble of claim 1 suchthat it is constructed in a liquid-tight fashion and its housing partscan be plugged into one another and withdrawn from one another with alow expenditure of force.

This object is achieved by means of the features specified in thecharacterizing part of claim 1.

When such a plug-and-socket connection is plugged together, the plug-inforce is composed of a plurality of components. Depending on thestructure of the housing parts and number of instances of contacting,the system can be closed only with extreme expenditure of force. Theparticular configuration of the sealing member and of the insertionsection contributes to the force reduction. The housing parts areprotected against the ingress of liquid by two annular lamellae ofdifferent diameter. The low number of lamellae and the combination of alamella seal and a compression seal permit sealing which is low infriction. Moreover, the short path on which the annular lamellae comeinto contact with the housing wall ensures good pressure balancing, withthe result that in this regard only low forces need to be expended. Thismeasure also has a positive effect during decoupling of theplug-and-socket connection. The housing parts can easily be separatedfrom one another, since the pressure difference is extremely slight.

According to the invention, the plug-in force is substantially reducedowing to the fact that the structure of the housing parts is selectedsuch that the force components do not add together but occursequentially, resulting in a virtually constant expenditure of forceover the entire displacement path at a low level. Referred to the pathcovered during the plugging-together, the mutual insertion of thecontact parts and the inception of the locking of the housing areperformed in a short displacement. After the insertion forces have beenovercome, a constant but low contact force is required for the furtherdisplacement of the contact parts. The maximum force to be expended tolock the housing occurs in the meantime. After said maximum has beenpassed, the final locking is performed automatically as it were, withthe aid of the pre-stressing, with the result that the friction forcesthen first occurring for the sealing do not raise the overall forcelevel. The relief of the latching means and the sealing process whichtakes place at the same time compensate one another with respect to theexpenditure of force.

In the relief of the latching means, the first housing part is displacedinto the final position in the second housing part. The latching meansconsist in principle in each case of a projection, beveled on bothsides, which cooperates with an opening arranged, for example, on an armof the other housing part. The relief takes place after the maximumdeflection of the arm has passed, which arm then slides, with theadvance of the first housing part, into the second housing part alongthe inclined bevel. In order to optimize the plug-in force, sealingtakes place only on this short part of the displacement path.

The material for the sealing member, in particular for the annularlamellae, must have good sealing properties and good sliding properties.Silicone fulfills these contrary demands best.

In order to facilitate the handling of the sealing member duringassembly, it is constructed with three annular lamellae. Only twoannular lamellae are required for the sealing function, although it mustbe ensured that the annular lamella with the smaller diameter faces thesocket region of the second housing part. Since the difference isdiameter can be discerned only with difficulty by the human eye, giventhe small overall dimensions of the sealing member, a third annularlamella has been arranged in addition in order to avoid faultyplugging-in. The result is a symmetrical structure, the sealing memberthus being plugged without a code.

The difference between the lamella diameters is advantageously in therange around 1 mm and is a function of the angular position of theinsertion section. This insertion section is kept as short as possiblewith reference to the assembly path so that the force component for theplacement of the seal becomes effective only over a short distance ofthe insertion path. As a result, this component can be integratedoptimally in the force characteristic in order to obtain a force levelwhich is low overall. It is particularly advantageous from this aspectto step the insertion section. Each lamella is given its specific rangeof action and therefore causes only the expenditure of force which isabsolutely necessary.

The invention will now be explained with reference to an exemplaryembodiment and with the aid of the drawings, in which

FIG. 1 shows the plug-and-socket connection in a longitudinal section;

FIG. 2 shows the housing parts in a longitudinal section during thefirst contact of the sealing member with the second housing part;

FIG. 3 shows an enlarged part section in accordance with FIG. 2;

FIG. 4 shows the housing parts in a longitudinal section in their lockedend position;

FIG. 5 shows an enlarged part section in accordance with FIG. 4;

FIG. 6 shows a diagram of the characteristic of the plug-in force of aconventional plug-and-socket connection; and

FIG. 7 shows a diagram of the characteristic of the plug-in force of aplug-and-socket connection according to the invention.

In the exemplary embodiment described below, only the componentsessential to the invention are provided with reference numerals. FIGS.1, 2 and 4 represent a plug-and-socket connection 1 to a scale of 2.5:1,while a scale of 5:1 is realized in FIGS. 3 and 5. The electricalplug-and-socket connection 1 comprises a first housing part 2 and asecond housing part 3. Arranged in the first housing part 2 is a contactpart 4 whose tip 5 projects into a socket region 6. This socket region 6serves to receive the second housing part 3 and is constructed for thispurpose with an insertion section 7 of specific construction.

The second housing part 3 comprises a cylindrical part 8, in which acontact part 9 is arranged, and a housing shell 10 surrounding thecylindrical part 8. A hollow cylindrical sealing member 11 isconstructed on the outside with three annular lamellae 12, 13 and 14 ispushed onto and fastened on the cylindrical part 8, the middle annularlamella 13 having a larger diameter D1 than the two outer annularlamellae 12 and 14, which are of the same size and have the diameter D2.Only the two annular lamellae 12 and 13 with the different diameters D1and D2 are required for the sealing function. The third annular lamella14, which likewise has a small diameter D2, serves exclusively toproduce a symmetrical lamella structure, in order to facilitate assemblyin which end is relevant. When the two housing parts 2 and 3 are beingplugged into one another, an opening 15 in the housing shell 10 and anopening 16 in a deflectable arm 17 cooperate with projections 18 and 19,beveled on both sides, on a housing wall 20 of the first housing part 2.

The plugged together of the two housing parts 2 and 3 is explained inmore detail below.

In FIG. 1, the second housing part 3 is inserted so far into the firsthousing part 2 that the cylindrical part 8 projects into the socketregion 6, and the housing shell 10 and the arm 17 butt against theprojections 18 and 19. The contact parts 4 and 9 do not yet touch oneanother. The force previously requiring to be expended servesexclusively to overcome the sliding friction between the housing shell10 and the arm 17 and the housing wall 20.

In the position in accordance with FIG. 2 and FIG. 3, the second housingpart 3 is pushed further into the first housing part 2. The tip 5 of thecontact part 4 is already inserted into the contact part 9 and has thusconcluded the insertion movement, which is expensive in terms of force.As the operation of assembling the contact parts 4 and 9 is continued,only slight friction forces remain to be overcome. The housing shell 10and the arm 17 were deflected to a maximum extent by the beveledprojections 18 and 19. If this process of movement is considered fromthe aspect of force alone, two rising force components are added to oneanother of which the contact force of the contact parts 4 and 9 fallsaway and remains at a uniform level, while the locking force hasstrongly increased. At this point in time, the sealing member 11 has apoint of contact with the first housing part 2 for the first time, butdoes not yet go over into the balance of forces.

FIGS. 4 and 5 represent the two housing parts 2 and 3 in their endposition, that is to say the plug-and-socket connection has beencompleted. The projections 18 and 19 are situated in the openings 15 and16 and lock the housing parts 2 and 3. The contact part 4 is completelyinserted into the contact part 9. The sealing member 11 is situatedbetween the cylindrical part 8 and the housing wall 20 and prevents theingress of liquid between the housing parts 2 and 3. By contrast withFIG. 2, the second housing part 3 has been pushed completely into thefirst housing part 2, the arm 17 and the housing shell 10 coming to restin a quasi automatic fashion owing to the restoring forces with theassistance of the beveled projections 18 and 19. The annular lamellae 12and 13 of th sealing member 11 first come into contact with thecircumferential insertion section 7 in the socket region 6 of the firsthousing part 2 at the moment when the restoring forces are released.

The insertion section 7 is stepped. A bevel 22 is located between twosteps 21 and 23. The first step 21 permits the sealing body 11, and thusthe second housing part 3, to be advanced easily, since the diameter D3of the first step 21 is equal to the diameter D1 of the middle annularlamella 13, while the front annular lamella 12 advances bearing againstthe bevel 22 and is slightly deformed. Upon further advance, the middleannular lamella 13 slides along the first step 21 into the bevel 22 andis arcuately deflected opposite to the plug-in direction. The frontannular lamella 12 goes over from the bevel 22 to the second step 23.The diameter D4 of the step 23 is smaller than the diameter D2 of theannular lamella 12. The annular lamella 12 is therefore stronglycompressed there. In this position, the outer locking of the housingparts 2 and 3 is concluded, and the plug-and-socket connection isproduced completely. During the displacement, the air located in andbetween the housing parts 2 and 3 is pushed past along the insertionsection 7 and the sealing member 11, thus ensuring satisfactory pressurebalancing. The locking is therefore performed without difficulty fromthis aspect as well. Moreover, it also supports the decoupling, sincethere is no need to remove a sealing member 11 which has been suckedtight. In order to seal the plug-and-socket connection 1 in the lineinsertion region as well, appropriate line seals 24 are used there.

FIGS. 6 and 7 reveal the difference between the force components of aconventional plug-and-socket connection with a lamella seal and aplug-and-socket connection 1 according to the invention. Comparableforce components are denoted here by the same letters, although theforce components of the conventional plug-and-socket connection areadditionally provided with an apostrophe. The characteristic of thecontact forces A and A' between the contact parts is the same for thetwo plug-and-socket connections over the entire displacement path B.During the insertion of the contact parts into one another, the contactforces A and A' rise strongly and thereafter fall off to a constantlylow level. The sealing force B' of the conventional plug-and-socketconnection has already started before the contact force A' and risescontinuously. Moreover, the latching force C' is added to this startingfrom half of the displacement path S, resulting in the production of astrongly rising plug-in force D' which does not drop until directlybefore the end position of the plug-and-socket connection by relief ofelastic latching means.

By contrast, the latching force C of the plug-and-socket connection 1according to the invention already occurs in a slightly rising fashionbefore the contact force A (FIG. 7). Up to the maximum deflection of thelatching means, the resulting plug-in force D is formed only from thelatching force C and the contact force A. The sealing force B does notoccur until the relief of the elastic latching means. The sealing forceB is overcompensated by the latching force C released, with the resultthat the plug-in force D drops in conjunction with a constant contactforce A. Distribution of the force-generating devices over the completedisplacement path S of the plug-and-socket connection 1 results in aliquid-tight connection with the minimum expenditure of force. Thisadvantage is effective, in particular, in the case of multipoleplug-and-socket connections, since there the plug-in force rise withincreasing number of poles.

    ______________________________________    List of reference symbols:    ______________________________________     1           plug-and-socket connection     2           first housing part     3           second housing part     4           contact part     5           tip     6           socket region     7           insertion section     8           cylindrical part     9           contact part    10           housing shell    11           sealing member    12           annular lamella with diameter D2    13           annular lamella with diameter D1    14           annular lamella with diameter D2    15           opening    16           opening    17           arm    18           projection    19           projection    20           outer wall    21           first step with diameter D3    22           bevel    23           second step with diameter D4    24           line seal    A            contact force    A'           contact force    B            sealing force    B'           sealing force    C            latching force    C'           latching force    D            plug-in force    D'           plug-in force    S            displacement path    ______________________________________

What is claimed is:
 1. An electrical plug-and-socket connectioncomprising a first housing part (2) with a socket region (6),comprisinga second housing part (3) with a cylindrical part (8) which can bereceived in the socket region (6), latching elements (15, 16, 18, 19)which are constructed on the first housing part (2) and on the secondhousing part (3), the latching elements (15, 16, 18, 19) includingprojections (18, 19) having beveled on both sides and engageable incomplementary openings (15, 16) formed in a flexible arm of one of thehousing parts, mateable electrical contacts arranged in the firsthousing part (2) and in the second housing part (3), a hollowcylindrical sealing member (11) which can be pushed onto the cylindricalpart (8) and which is constructed on the outside with at least twoflexible annular lamellae (12, 13) which are of different diameter (D1,D2) and extend in the radial direction, wherein, the socket region (6)is constructed with a stepped conical insertion section (7), the annularlamella (12) with the smaller diameter (D2) faces the first housing part(2) and is radially compressed between the housing wall (20) thereof andthe sealing member (11), and the annular lamella (13) with the largerdiameter (D1) acts as a lamella seal against the stepped conicalintersection section, and wherein the latching elements (15, 16, 18, 19)are arranged on the housing parts (2, 3) so that upon mating the firstand second housing parts the flexible arm first engages the beveledprojections so that the arm is deflected by the projections and uponfurther axial movement of the housing parts in the mating direction theflexible arm reaches a maximum deflection with an associated increase ininsertion force and thereafter upon still further axial movement of thehousing parts the insertion force is reduced and so that the initialcontact of the two annular lamellae (12, 13) with the insertion section(7) takes place after the maximum deflection of the flexible arm hasoccurred.
 2. The electrical plug-and-socket connection as claimed in oneof claim 1, wherein the sealing member (11) including the annularlamella (12, 13) consists of silicone.
 3. The electrical plug-and-socketconnection as claimed in one of claim 1, wherein the diameter (D1) ofthe larger annular lamella (13) is larger by at least 1 mm than thediameter (D2) of the smaller annular lamella (12).
 4. The electricalplug-and-socket connection as claimed in one of claim 1, wherein thesealing member (11) has three annular lamellae (12, 13, 14), the middleannular lamella (13) having a larger diameter (D1) than the outerannular lamellae (12, 14), which are of the same size.